As a safety issue, permanent magnetic (PM) motors/generators must be properly maintained. Any cracks developed in the PM rotors over time must be identified at an early stage in crack development. Although crack inspection devices are known and can be used to detect cracks in rotors, such inspections are usually only available when the rotors are not in operation and the inspection procedure may require the rotor to be disassembled from the rotor machine.
Accordingly, there is a need to provide an improved technique and apparatus for permanent magnetic rotor crack detection.